linux-kernel - Re: [PATCH v7 2/4] driver core: add deferring probe reason to devices

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Message-ID: <a48ab93c-0d9c-ed8b-76dd-62007826bf6f@samsung.com>
Date:   Tue, 30 Jun 2020 10:32:06 +0200
From:   Andrzej Hajda <a.hajda@...sung.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Jernej Skrabec <jernej.skrabec@...l.net>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Mark Brown <broonie@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH v7 2/4] driver core: add deferring probe reason to
 devices_deferred property


On 29.06.2020 18:36, Andy Shevchenko wrote:
> On Mon, Jun 29, 2020 at 2:22 PM Andrzej Hajda <a.hajda@...sung.com> wrote:
>> /sys/kernel/debug/devices_deferred property contains list of deferred devices.
>> This list does not contain reason why the driver deferred probe, the patch
>> improves it.
>> The natural place to set the reason is dev_err_probe function introduced recently,
>> ie. if dev_err_probe will be called with -EPROBE_DEFER instead of printk the message
>> will be attached to deferred device and printed when user read devices_deferred
> to a deferred
>
> reads
OK, thx.
>
>> property.
> ...
>
>> @@ -3984,10 +3986,12 @@ int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)
>>          vaf.fmt = fmt;
>>          vaf.va = &args;
>>
>> -       if (err != -EPROBE_DEFER)
>> +       if (err != -EPROBE_DEFER) {
> Why not positive conditional? (Okay, I'm fine with either in this case)


I put more natural branch 1st.


>
>>                  dev_err(dev, "error %d: %pV", err, &vaf);
>> -       else
>> +       } else {
>> +               device_set_deferred_probe_reson(dev, &vaf);
>>                  dev_dbg(dev, "error %d: %pV", err, &vaf);
>> +       }
> To reduce churn, you may move {} addition to the first patch.


But then I need to explain why it is there :)


>
> ...
>
>>          list_for_each_entry(curr, &deferred_probe_pending_list, deferred_probe)
>> -               seq_printf(s, "%s\n", dev_name(curr->device));
>> +               seq_printf(s, "%s\t%s", dev_name(curr->device),
>> +                          curr->device->p->deferred_probe_reason ?: "\n");
> Hmm... "\t" will be dangling in the latter case


Hmm, I followed your advice [1] :)

[1]: 
https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1787370.html


Regards

Andrzej


>